Indications of gas-hydrate dissociation caused by sea level rise off Ilulissat Icefjord, Greenland

• Main Authors: Schumann, Kai, Weinrebe, Wilhelm, Völker, David, Kuijpers, Antoon
• Format: Conference Object
• Language: unknown
• Published: 2010
• Subjects: Arctic; Greenland; Ilulissat; Kongsberg; Antarc*; Antarctica; Iceberg*
• Online Access: https://oceanrep.geomar.de/id/eprint/10855/; http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=table&application=fm10&convert=&converthl=&refinequery=&formintern=&formextern=&transquery=ilulissat&_lines=&multiple=0&descriptor=%2fdata%2fepubs%2fwais%2findexes%2ffm10%2ffm10%7C6

C23B-0603 Ilulissat Icefjord in West-Greenland is the fastest and most productive iceberg calving area outside Antarctica. Changes in climate exert a first-order control on the recession of the icefront and the calving of the icebergs. Glacial and geological processes related to iceberg calving and transport shape the morphology of the seafloor in the area characteristically. Revealing the morphology by high-resolution bathymetric mapping helps to understand these processes. During a cruise with RV Maria S. Merian in summer 2007 large parts of the area were mapped with Kongsberg EM120 and EM1002 multibeam systems. This data was complemented by a survey using a portable Seabeam 1180 multibeam system temporarily mounted on the small local vessel Smilla which could navigate through areas inside the icefjord inaccessible to large research vessels. A comprehensive image of the morphology of the area was achieved by compiling and merging both datasets. Different morphological features such as ridges, shaped like drumlins and valleys which could be connected to channel systems, directing debris flows to a deposition centre characterize the central part of the survey area. Here, a series of prominent circular features 80m to 150m in diameter and up to 30m deep have been found and are interpreted as pockmarks. A parasound sediment echosounder profile across one of the pockmarks documents the absence of the upper sedimentary unit inside. Furthermore, a blank zone in the central part indicates uprising fluids or gas. The northeast - southwest alignment of the pockmarks points to a formation related to slides, faults, and iceberg furrows. The depth of their occurrence indicates a formation by dissociating gas hydrates. The most recent active pockmarks are located in the centre and the northeastern end of the depression in a depth of 395m. The gas hydrate stability zone in arctic regions tapers out at around 400m at 3° bottom water temperature which coincides with the values measured with a CTD close to this position. The ...